Photoelectric method and apparatus for testing vacuum conditions in containers



Oct. 10, 1950 2,524,929

J. RAZEK PHOTOELECTRIC METHOD AND APPARATUS FOR TESTING VACUUM CONDITIONS IN. CONTAINERS Filed Feb. 21, 1946 f, INDICATOR Patented Oct. 10, 1950 PHOTOELECTRIC METHOD AND APPARATUS FOR TESTING VACUUM CONDITIONS IN CONTAINERS Joseph Razek, Llanerch, Pa., assignor to Wm. S. Scull Company, Camden, N. J., a corporation of New Jersey Application February 21, 1946, Serial No. 649,254

8 Claims. 1

My invention has to do with the packaging of various products in evacuated containers and particularly with a method and apparatus for determining if proper vacuum conditions exist in the container after it has been packed and sealed.

The containers in use for packaging of food products, such as cofiee for example, in a vacuum are generally metal cans or glass jars with metallic caps, so that in either case one end closure of the container is, in eifect, a flexible metallic diaphragm. When there is atmospheric pressure in the container, the end closure or lid will be flat. However, when proper vacuum conditions exist in the containers, the unsupported portion of the lid will be dished in or forced by the external air pressure to assume a concave shape, forming in effect a rough concave mirror having the property of reflecting and concentrating parallel light beams at a focal point located at a distance from the lid equal to one-half of the radius of the curvature of the surface.

When the lid is flat, however, the reflected light beam is not concentrated and the unit intensity of the reflected beam is, on the average, no greater than that of the impinging beam.

It is the primary object of my invention to provide a method and apparatus for determining pressure conditions in the container by reflecting a light beam from a flexible light reflecting section of the container, the surface contour of which will vary with variations of pressure conditions in the container. It is a further object of my invention to provide a method and apparatus for determining vacuum conditions in a container by reflecting light from a flexible light reflectin section of the container which will be flat when there is atmospheric pressure in the container but will assume a dished-in or concave shape when proper vacuum conditions obtain within the container.

It is a further object of my invention to provide a method and apparatus whereby, in a moving line of containers, those having improper pressure conditions within the container will be automatically rejected from the line.

Another object of my invention is to provide an apparatus for rejecting from a line of containers those having improper pressure conditions by re- 2 A form of suitable apparatus is also illustrated in the accompanying drawingswherein:

Figures 1a and lb are diagrammatic views illustrating the effects of variations of surface contour of a flexible light reflecting section of a con- 7 tainer, in reflecting a light beam;

Figure 2 is a diagrammatic illustration of an apparatus for giving visual or audible indication of pressure conditions in a container;

Figure 3 is a diagrammatic illustration of an automatic device for detecting and rejecting improperly evacuated containers from a line thereof moving on a conveyor belt; and

Figure 4 is a plan view of a part of the apparatus illustrated in Figure 3.

Referring now to the drawings:

In Figures 1a and 1b, reference numeral 21 indicates a jar or other container with a lid or cover I having a flexible light reflecting section 2. A beam of light 3 is directed onto section 2 and is reflected thereby onto a screen 6 having an aperture 4. Under conditions of substantially equal pressures within and without the jar, the flexible section of the cover will be flat, as shown in Figure 1a, and only a small part of the light will penetrate the aperture 4, and fall on the photo-electric cell 5. Under the conditions illustrated in Figure 11), on the other hand, the jar is represented as evacuated, with the result that the flexible section 2 has been forced by the pressure of the atmosphere to assume a concave contour, focusing the reflected light so that all or most of the light passes through the aperture 4 and falls on the photo-electric cell 5. By placing the screen 6 at a distance from the jar equal to the focal length of the mirror formed by the flexible section of the cover at the pressure determined to be desirable, the amount of light falling on the photo-electric cell will be at a maximum when ideal pressure conditions obtain in the jar.

I have found that the difference in the amount of light reflected under the different conditions illustrated in Figures la and 1b is a reliable practical indication of pressure conditions in containers in which various products are vacuum packed and in Figure 2 I have diagrammatically shown an application of the principle to the inspection of a moving line of containers with provision for automatic indication of those in which the pressure is not proper,

In Figure 2, reference numeral I indicates the source of a light such as a light bulb from which light is directed on to the flexible section 2 of the lid I of'the jar 21 by a mirror 8. As in Figure 1, reference numerals 6 and 5 indicate a 3 screen and photo-electric cell, respectively. The jars 21 are arranged in a line on the conveyor belt 28 in such a position that the light beam 3 reflected from mirror 8 will strike the jar at a predetermined point and reflect the light through the aperture 4 onto the photo-electric cell 3.

Connected to the photo-electric cell I is an indicating device 33 which may take the form of a bell or a light arranged to operate when the light reflected onto the photo-electric cell 3 from the flexible section 2 of the lid i is either more, less than, or equal to some predetermined standard. The operation of such devices by photoelectric cell is well understood in the art and will not be described here. If desired, a meter could be substituted for the light or bell and indications of vacuum conditions in the container would be registered by the meter in accordance with the intensity of the light reflected on the photo-electric cell, which would, of course, be governed-by the amount of curvature of reflecting surface 2.

In Figure 3, I have illustrated an application of the principle in a case where it is desired to inspect and reject from a conveyor line of evacuated jars those jars in which the vacuum has been broken, 1. e., to reject all jars whose internal pressure is atmospheric.

In the packaging of coffee, for example, the jars of coffee are passed through an evacuating apparatus (not shown) in which the air is evacuated from the jar and the lid screwed on tightly when the jar is being evacuated. In many cases, due to imperfections in the lid or improper operation of the evacuating apparatus, for example, Jars would be delivered ontothe conveyor line in which the vacuum has not been produced or, it produced, has been broken. In the apparatus illustrated, the jars 21 are delivered from the evacuating apparatus onto a continuous conveyor belt 28. At a predetermined point along the conveyor belt, the-jars reach a position where the light 3 coming from a lamp 1 and reflected by mirror 8 will strike the top of the Jar. In order to insure proper positioning of the jars laterally of the conveyor belt guide, rails 34 are provided on either side of the line of moving jars as they approach the light beam 3.

The screen 5, having an aperture 4, is mounted in such position that when a jar is in proper position under the incident light beam 3 the aperture 4 is approximately in the region of maximum light intensity at the focal point of the spherical surface 2 of an evacuated jar. Mounted behind this aperture is the photo-electric cell 5 energized by a battery 31.

Mounted to one side and immediately below the impinging light beam 3 is a rejection solenoid 9, whose plunger ill will kick an imperfectly evacuated jar oil the conveyor belt 28 which is assumed to move into the plane of the paper. The rejected jar will then slide down a slide 29 and away from the conveyor system.

The operation of the solenoid 9 is controlled as follows: The four-element gas-filled rectifier tube 22. known as a Thyratron, is energized by alternating current. Lead 25, connected to a source of alternating current, is connected to the cathode of the tube. Lead 26, also connected to the source of alternating current, is connected to the plate of the tube 22 through the solenoid 9 and lead 24. When the grid of the tube 22 is positively charged, the tube is in conducting position and the solenoid is activated. Since alternating current is supplied to the tube 22, it will 4 be sell-extinguishing and will flre only so long as the grid thereof is maintained positive with respect to the cathode.

A mirror II and another photo-electric cell i2 are so arranged that light 1mm the lamp 1 will be reflected from mirror 3 onto the mirror II in such a way that light will pass to photoelectric cell l2 through two horizontally separated apertures 33 in the screen 33, unless the beams are interrupted by the presence 0! the jar 21 on the conveyor belt. The two horizontally spaced apertures u are employed in order to reduce the time during which the light passing from mirror II to photo-electric cell i2 is interrupted to a period comparable to the time during which light is reflected from the lid 2 through the aperture 3 onto the photo-electric cell 5. The horizontal distance between the apertures will be slightly less than the diameter of the lid of the containers and both apertures will have m be blocked by the jar in order to prevent light falling through one or the other onto the photo-electric cell l2.

The portion of the circuit just described is known as a positioning circuit and is necessary in order to properly phase the various operations of the apparatus as will be seen from the following. The photo-electric cell i2 is connected to the grid of vacuum tube i3 through lead 3| and to the cathode through lead 32 and battery l6 and potentiometer it so that whenever light strikes the cell through either of the apertures 36, the vacuum tube l3, which is a conventional triode, will not pass any current. This results because whenever light falls on photo-electric cell 12 through either aperture 33 a negative bias derived from battery It is placed on the grid of the vacuum tube l3. when light to the photo-electric cell is completely interrupted, however, the negative bias on the grid of tube I3 is removed, allowing potential on the grid of vacuum tube l3 to assume a suflicient po itive potential to permit the vacuum tube i3 to pass current. The grid resistor 21 connected to the grid of vacuum tube i3 is of sumcient magnitude to permit complete cut-off of the current through vacuum tube l3.

The plate circuit of this tube includes plate resistance I1 and battery l8. This plate resistance i1 is also a part of grid bias resistance of vacuum tube 20 which is also a conventional triode. Vacuum tube 20 has its grid, which is biased in part by an appropriate grid resistance i8, connected to photo-electric cell 5. The plate circuit of vacuum tube 20 is in turn connected to resistor 23 and is energised by battery 2|. The resistor 23 is also the grid resistor for the tube 22. The potentiometer l4 and battery It provide means of adjusting the bias on the grid of vacuum tube i 3.

Suppose now that there is no jar intercepting the light beam from mirror II to photo-electric cell l2. There would, therefore, be a strong light on photo-electric cell l2 and no light on photoelectric cell 5. The strong light on photo-electric cell l2, which is energized by battery II, will result in the blocking of tube l3 with the result that no current flows through resistor l1, supplied by battery i3. Consequently, the grid of tube 20 will be essentially the potential of its cathode, viz., the same as the negative terminal of the battery 2|. This will result in a fairly large plate current flowing through resistor 23, supplied by battery 2 i. The potential drop across resistor 23, which is also connected between the grid of tube 22 and its filament, will result in a substantial negative potential applied to the grid of tube 22 and, hence, this will be in a nonconducting state and no current will flow through the lead 24 and the solenoid 9.

Suppose now a jar comes between the mirror I l and the screen 35, interrupting the light to both apertures 36 and, for the purpose of illustration, assume that the aperture 4 in screen 6 is closed. At the instant when light to both apertures 36 is interrupted completely, photo-electric cell l2 will receive no light and because of the method of connection-viz., the anode connected to the grid-a substantial plate current will be passed by tube l3 supplied by the battery l8 and passed through resistor l'l. This will result in a substantial voltage drop across the resistor I! with the result that the grid resistor l9, connected to the grid of tube 20, will receive a negative potential reducing substantiall the current passed by the tube 20. This stoppage, or reduction, of the current passed by tube 20 will reduce the potential drop across the resistor 23. By proper proportioning of the resistances, this reduction in bias will be sufficient to make the grid of the tube 22 positive so that the tube 22 will become conducting, allowing a large amount of current to flow through the lead 24 andthrough the solenoid 9, This will violently energize the solenoid causing plunger ill to move out and kick the jar 21 at right angles to the conveyor belt and onto the slide 29. In other words, in the absence of any other action, a Jar would be kicked out by the solenoid it every time it interrupted the beam to apertures 36.

But, now, suppose that the aperture I is opened so that light reflecting from the lid i passes to the photo-electric cell 5. When the center portion of the cap 2 is fiat, which is the case when the jar is not evacuated, the amount of light falling on the photo-electric cell is not sufllcient to alter the action above described. But if the jar is evacuated, the center portion of the lid I will be concave and, consequently, the light will be concentrated in aperture 4 resulting in a. much larger amount of light impinging on photo-electric cell 5. This greater amount of light passing through the photo-electric cell will be sufllcient to maintain the grid of tube 20 positive so that current will flow through this tube and, hence, through resistor 23, even though the tube I2 is passing current. Therefore, if such is the case, the tube 22 will remain non-conducting because of the fact that tube 20 passes current, resulting in a negative voltage applied to the grid of the tube 22.

In other words, even though the light falling on photo-electric cell [2 is interrupted resulting in a passage of current by the tube 13, which would make the grid of the tube 2|! negative, this negative condition is prevented by the increase in current passing from the photo-electric cell 5 to the same grid. This increase of current, however, will only take place if the jar 21 is evacuated which in turn results in an increase of light to the photo-electric cell 5. Adjustment of the various resistances and potentials is such that a flat center portion in the cap, indicated by 2, will not result in enough light passing to photoelectric cell 5 to maintain the proper current through tube 20. Therefore, the solenoid 9 will be energized whenever a jar interrupts the beam from mirror II to photo-electric cell I2, unless there is enough signal impinging on photo-electric cell I to keep the tube 22 from firing.

, zontal.

(iii

In the arrangement illustrated in the drawings, I have shown the light striking the top of the container at about an angle of 45 from the hori- In practice, I have found this a convenient angle but it will be understood that it is not necessary to use the angle illustrated and practically any angle from the horizontal included in an arc of could be used with more or less effective results.

I have found that the apparatus above described, illustrated in Figures 3 and 4, operates in a quite satisfactory manner to inspect and reject from a moving line of containers those in which vacuum conditions are not satisfactory. One method used heretofore to inspect containers has been to tap the lid with a metal hammer. The pitch of the resulting sound will give a general indication of the vacuum conditions within the jar. However, on reinspecting containers which have been tested in this manner on apparatus above described, I have found that many jars which would pass the test of the tapping with the metallic hammer are rejected and that the vacuum conditions in such rejected containers is not satisfactory.

It will be understood that other arrangements of photo-electric cells, vacuum tubes and electrical circuits could be devised to utilize the principle of the reflected beam of light in the testing of jars for vacuum conditions, and it will be understood that I do not limit myself to the detailed arrangement of such apparatus described above.

I claim:

I. In the art of packaging products in containers in a vacuum, the containers having a flexible, light reflecting section which will assume a concave form under the influence of vacuum in the container, the method of rejecting from a line the containers in which the pressure is atmospheric, comprising passing the containers in the path of two light beams, one of which conditions a rejector element to reject the container and the other of which conditions another element located substantially at the focal point of reflection of the beam when desired vacuum conditions exist to prevent operation of the rejector.

2. Apparatus for automatically inspecting containers having a flexible, light reflecting section which will assume a concave shape under the influence of vacuum in the container comprising a conveyor on which said containers are placed, a source of light adapted to direct a beam onto the said light reflecting section of the containers as they pass a predetermined point, a photo-electric cell located substantially at the focal point of reflection of the beam when the desired vacuum exists in the container, a rejection member controlled by said photo-electric cell and means to condition said rejection member for operation only when the container is in position for inspection.

3. Apparatus for automatically inspecting containers having a flexible, light reflecting section which will assume a concave shape under the influence of vacuum in the container, comprising a conveyor on which saidcontainers are placed, a source of light adapted to direct a beam onto the said light reflecting section of the containers as they pass a predetermined point, a photo-electric cell located substantially at the focal point of reflection of the beam when the desired vacuum exists in the container, a rejection member controlled by said photo-electric cell and means to condition said rejection member for operation only when the container is in position for inspection. comprising a second photo-electric cell and a source oi light adapted to direct a beam thereon. said photo-electric cell being so positioned that said beam will be interrupted by the containers as they pass said predetermined point.

4. Apparatus for automatically inspecting containers having a flexible, light reflecting section which will assume a concave shape under the influence of vacuum in the container, comprising a conveyor on which said containers are placed, a source of light adapted to direct a beam onto the said light reflecting section of the containers as they pass a predetermined point, a photo-electric cell located substantially at the focal point of reflection oi the beam when the desired vacuum exists in the container, a rejection member controlled by said photo-electric cell and means to condition said re ection member for operation only when the container is in position for inspection, comprisin a second photo-electric cell and a source of light, a screen having horizontally spaced apertures through which said light passes before striking said second photoelectric cell, said screen being so located that the light to both apertures will be interrupted by the containers only as they pass said predetermined point.

5. Apparatus for automatically inspecting containers having a flexible, light reflecting section which will assume a concave shape under the influence of vacuum in the container, comprising a conveyor on which said containers are placed, a source of light adapted to direct a beam onto the said light reflecting section of the containers as they pass a predetermined point, a photo-electric cell located substantially at the focal point of reflection of the beam when the desired vacuum exists in the container, a rejection member controlled by said photo-electric cell and means to condition said rejection member for operation only when the container is in position for inspection, comprising a second photo-electric cell and a source of light, a screen having horizontally spaced apertures through which said light passes before striking said second photo-electric cell, said screen being so located that the light to both apertures will be interrupted only when the container is in position for inspection.

6. Apparatus for automatically inspecting containers having a, flexible, light reflecting section which will assume a concave shape under the influence of vacuum in the container, comprising a conveyor on which said containers are placed, a source of light adapted to direct a beam onto said light reflecting section of the containers as they pass a predetermined point and adapted to direct another beam toward said containers as they pass said point, a rejection member adapted to move containers from the conveyor, a light responsive device located substantially at the focal point of reflection of the beam when the desired vacuum exists in the container and adapted to control operation of said rejection member and a second light intensity operated 8 device toward which said second beam is directed and adapted to condition said rejection member for operation when said second beam is interrupted.

'1. 1n the art of packaglnl pr ucts in containers in a vacuum, means to inspect and reject from a moving line or containers those in which the vacuum conditions are unsatisfactory, comprising a, conveyor for said containers, a solenoid operated rejection plunger adapted to push containers oi! the conveyor and means to control the operation of said solenoid, comprising a light intensity operated device, means to direct a light beam onto the lid of the containers to reflect onto said device as the containers pass a point oi inspection, said light intensity operated device being located substantially at the focal point of reflection oi the beam when the desired vacuum exists in the container and an electronic tube controlled by said device and adapted to control the flow 0t energizing current to the solenoid.

8. In the art of packaging products in containers in a vacuum, means to inspect and reject from a moving.line of containers those in which the vacuum conditions are unsatisfactory, comprising a conveyor for said containers, a solenoid operated rejection plunger adapted to push containers of! the conveyor and means to control the operation of said solenoid comprising a light intensity operated device, means to direct a light beam onto the lid of the containers to reflect onto said device as the containers pass a point of inspection, said-light intensity operated device being located substantially at the focal point of reflection of the beam when the desired vacuum exists in the container and an electronic tube controlled by said devices and adapted to control the flow of energizing current to the solenoid; and means to condition the tube to pass said energizing current comprising a second light intensity operated device, means to direct a second beam of light onto said second device from such position that the beam will be interrupted when a container is in position for inspection, said second device conditioning the tube to pass energiz ing current to the solenoid only when said second beam is interrupted.

JOSEPH RAZEK.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 1,766,019 Garrett June 24, 1930 2,027,595 Knobel Jan. 14, 1936 2,067,262 Demontvignier Jan. 12, 1937 2,142,920 Rose Jan. 3, 1939 2,164,576 Collins July 4, 1939 2,280,948 Gulliksen Apr. 28, 1942 FOREIGN PATENTS Number Country Date 405,243 British Apr. 28, 1932 

